Catalytic dehydrogenation processes and chromium catalysts for use therein

ABSTRACT

A chromium catalyst is disclosed for use in dehydrogenation and dehydrocyclization processes.

FIELD OF THE INVENTION

[0001] The present invention relates to a novel catalyst comprisingchromium and its use in dehydrogenation or dehydrocyclization of C₂₋₁₀hydrocarbon processes.

BACKGROUND OF THE INVENTION

[0002] The dehydrogenation of paraffins to olefins is commerciallysignificant because of the need for olefins for the manufacture of highoctane gasolines, elastomers, detergents, plastics, ion-exchange resinsand pharmaceuticals. Important hydrocarbon dehydrocyclization reactionsare the conversion of diisobutylene and isooctane to p-xylene.

[0003] Processes for the conversion of paraffin hydrocarbons to lesssaturated hydrocarbons are known. For example see U.S. Pat. No.4,513,162, U.S. Pat. No. 5,378,350 and European Patent Application No.EP 947,247. Nonetheless, there is a continuing need to develop newcatalysts which are more effective or otherwise improved for use indehydrogenation processes.

SUMMARY OF THE INVENTION

[0004] Disclosed herein is a composition having the formulaCr_(a)A_(b)B_(c)(O_(1−z)(OH)_(2z))_(y), wherein a+b+c=1; wherein A is anelement selected from the group consisting of Zn, Sn, Rh, Li, Na, K, Rb,Cs, Be, Mg, Ca, Sr and Ba; B is at least one element selected from thegroup consisting of Al, Si and Mg; a is greater than 0.01 but less than0.5; b is greater than 0.01 but less than or equal to 0.5; c is greaterthan 0.2 but less than or equal to 0.999; y is determined by the sum ofthe oxidation states of Cr, A and B individually multiplied by thecorresponding stoichiometric coefficent a, b, or c, said sum thendivided by 2; and z is greater than or equal to 0 but less than or equalto 2.

[0005] This invention provides a process for converting at least one C₂to C ₁₀ hydrocarbon to less saturated hydrocarbons comprising the stepof contacting at least one C₂ to C₁₀ hydrocarbon with at least onecatalyst selected from the group consisting ofCr_(a)A_(b)B_(c)(O_(1−z)(OH)_(2z))_(y), wherein A is an element selectedfrom the group consisting of Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca,Sr and Ba; B is at least one element selected from the group consistingof Al, Si and Mg; a+b+c=1; a is greater than 0.01 but less than 0.5; bis greater than 0.01 but less than or equal to 0.5; c is greater than0.2 but less than or equal to 0.999; y is determined by the sum of theoxidation states of Cr, A and B individually multiplied by thecorresponding stoichiometric coefficent (a, b or c), and said sum thendivided by 2; and z is greater than or equal to 0 but less than or equalto 2; with a catalyst composition comprising rhodium and rare earthoxides; at a temperature of about 300° C. to about 650° C.

DETAILED DESCRIPTION OF THE INVENTION

[0006] The catalyst compositions of the present invention are of theformula Cr_(a)A_(b)B_(c)(O_(1−z)(OH)_(2z))_(y), wherein a+b+c=1; whereinA is an element selected from the group consisting of Zn, Sn, Rh, Li,Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba; B is at least one element selectedfrom the group consisting of Al, Si and Mg; a is greater than or equalto 0.01 but less than or equal to 0.5; b is greater than or equal to0.01 but less than or equal to 0.5; c is greater than or equal to 0.2but less than or equal to 0.999; y is determined by the sum of theoxidation states of Cr, A and B individually multiplied by thecorresponding stoichiometric coefficent a, b, or c, said sum thendivided by 2; and z is greater than or equal to 0 but less than or equalto 2 can be prepared by a variety of known art methods such asimpregnation, gel formation (including xerogel or aerogel formation),freeze-drying, spray drying, and spray roasting.

[0007] Impregnation

[0008] The impregnation technique typically comprises contacting acatalyst support with an aqueous solution of a compound of chromium anda solution of compounds containing elements A and/or B. For example, awater soluble chromium compound such as Cr(NO₃)₃.9H₂O can be impregnatedinto preformed oxides or oxyhydroxides of elements A and B (e.g.,MgSiO₃). The contacting is followed by drying and calcining thesupported materials. In some cases calcination can be accomplished insitu under reaction conditions.

[0009] Gel Formation

[0010] Pre-formed Colloidal Sol Destabilization: One or more inorganicmetal colloids may be used as starting material for preparing thecatalyst gels of the present invention. These colloids include colloidalalumina sols, colloidal silica sols or their mixtures. There are alsoseveral methods of preparing colloids, as described in “InorganicColloid Chemistry”, Volumes 1, 2 and 3, J. Wiley and Sons, Inc., 1935.The pre-formed colloidal sols are sold commercially and readilyavailable from Nyacol Products.

[0011] It is preferred that pre-formed colloidal sols in water, oraquasols, are used in the catalyst preparation for the dehydrogenationprocess invention disclosed herein. The aquasols are comprised ofcolloidal particles ranging in size from 2 nanometers to 50 nanometers.In general, the smaller primary particle sizes (2 nm to 5 nm) arepreferred. The pre-formed colloidal sols contain from 10 to 35 weight %of colloidal oxides or other materials, depending on the method ofstabilization.

[0012] In this invention, the colloids, which are originally stableheterogeneous dispersions of oxides and other species in solvents, aredestabilized to produce colloidal gels. Destabilization is induced, insome cases, by the addition of soluble salts, (e.g., chlorides ornitrates), which change the pH and the ionic strength of the colloidalsuspensions, by the addition of acids or bases, or by solvent removal.pH changes generally accompany the addition of soluble salts; ingeneral, this is preferred over solvent removal. Generally, a pH rangeof from about 0 to about 12 can be used to destabilize the colloids. Itis noted that very large extremes in pH (such as pH 12) can causeflocculation and precipitation. A pH range of from about 2 to 8 isgenerally preferred.

[0013] The medium used is typically aqueous, although non-aqueouscolloids can also be used. The additional metal or inorganic reagents(i.e., salts of Cr or the A and B components) used should be soluble inthe appropriate aqueous and non-aqueous media.

[0014] Sol-Gel Synthesis Using Alkoxides: The catalysts of the presentinvention can also be prepared by a sol gel process. One or more metalalkoxides (e.g., tetraethylorthosilicate) may be used as startingmaterial for preparing the gels. The inorganic metal alkoxides used toprepare the catalyst may include any alkoxide which contains from 1 to20 carbon atoms, preferably 1 to 5 carbon atoms, in the alkoxide group.It is preferred that these alkoxides are soluble in the liquid reactionmedium. C₁-C₄ alkoxides are most preferred. An example of a mostpreferred C₁-C₄ alkoxide is aluminum isopropoxide.

[0015] Commercially available alkoxides can be used. However, inorganicalkoxides can be prepared by other routes. Some examples include directreaction of zero valent metals with alcohols in the presence of acatalyst. Many alkoxides can be formed by reaction of metal halides withalcohols. Alkoxy derivatives can be synthesized by the reaction of thealkoxide with alcohol in a ligand interchange reaction. Direct reactionsof metal dialkylamides with alcohol also form alkoxide derivatives.Additional examples are disclosed in “Metal Alkoxides” by D. C. Bradleyet al., Academic Press, (1978).

[0016] A solution of a soluble salt comprising at least one metalselected from the group consisting of Cr, Al, Zn, Sn, Rh, Li, Na, K, Rb,Cs, Be, Mg, Ca, Sr and Ba (e.g., Cr(NO₃)₃, chromium acetate, chromiumhydroxide acetate, Al(NO₃)₃, Zn(NO₃)₂, Sn(NO₃)₂, RhCl₃, LiNO₃, NaNO₃,KNO₃, RbNO₃, CsNO₃, Be(N0₃)₂, Mg(NO₃)₂, Ca(NO₃)₂, Sr(NO₃)₂, andBa(NO₃)₂) is prepared. Other soluble salts (for example, acetates,chlorides, nitrates, nitrites) can also be used. An aqueous solutioncontaining at least one dissolved metal salt is added to a non-aqueoussolution of at least one alkoxide selected from the group consisting ofmagnesium, silicon, and aluminum alkoxides (e.g., magnesium methoxide,silicon tetraethylorthosilicate and aluminum isopropoxide) to induce ahydrolysis and condensation reaction of the alkoxides to form a gel. Thesolution is prepared in a moisture-free environment, preferably underinert conditions, for example a nitrogen blanket. It is also preferablethat the hydrolysis reactions to induce gel formation be performed undera moisture free, inert gas, environment so that the hydrolysis can becontrolled during the contacting step of the non-aqueous with theaqueous solutions. The material can be conventionally or supercriticallydried to produce a xerogel or aerogel.

[0017] Alternatively, the catalysts of the present invention can also beprepared by a sol gel process using non-aqueous solvents. A solution ofa soluble salt comprising at least one metal selected from the groupconsisting of Cr, Al, Si, Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca, Srand Ba soluble in non-aqueous media (e.g., Cr (acetylacetonate)₃,dissolved in ethanol and sodium ethoxide dissolved in ethanol) isprepared. A non-aqueous solution of at least one alkoxide selected fromthe group consisting of magnesium, silicon, and aluminum alkoxides(e.g., magnesium methoxide, silicon tetraethylorthosilicate and aluminumisopropoxide) is added to the soluble metal salt solution. The solutionis prepared in a moisture-free environment, preferably under inertconditions, for example a nitrogen blanket. It is desirable to controlhydrolysis and condensation by adding water so that one can inducegelation at the desired time. In a second step, water or other proticsolutions (for example ethanol) optionally containing at least onedissolved metal selected from the group consisting of Cr, Al, Zn, Sn,Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, and Ba, as described above, canbe added to induce hydrolysis and condensation reactions to form a gel.It is also preferable that the hydrolysis reactions to induce gelformation be performed under a moisture free, inert gas environment sothat the hydrolysis can be controlled during the contacting step of thenon-aqueous with the aqueous solutions. The material can beconventionally or supercritically dried to produce a xerogel or aerogel.

[0018] The solution medium used to make the gel generally should be asolvent for the inorganic alkoxide or alkoxides used, and the additionalmetal reagents and promoters which are added in the synthesis.Solubility of all components in their respective media (aqueous andnon-aqueous) is preferred. Solubility of all components results inhighly dispersed materials, which in turn results in catalyst metalparticles in the nanometer size range.

[0019] The addition of acidic or basic reagents to the inorganicalkoxide medium can have an effect on the kinetics of the hydrolysis andcondensation, and the microstructure of the oxyhydroxide matricesderived from the alkoxide precursor which entraps or incorporates thesoluble metal and promoter reagents. Generally, a pH within the range offrom 1 to 12 can be used, with a pH range of from 1 to 6 beingpreferred.

[0020] In the preparation of the compositions of the present inventionwater and any aqueous solutions are added in a dropwise fashion to thealcohol soluble alkoxide and other reagents to induce hydrolysis andcondensation. Depending on the alkoxide used, a discernible gel pointcan be reached in minutes or hours. The molar ratio of the total wateradded to total Mg, Si, and Al added (including water present in aqueoussolutions) varies according to the specific inorganic alkoxide.

[0021] Typically, the concentration of the amount of solvent used islinked to the alkoxide content. For example, a molar ratio of 26.5:1 ofalcohol (e.g., ethanol):total alkoxide can be used, although the molarratio of alcohol:total alkoxide can be from about 5:1 to 53:1, or evengreater. If a large excess of alcohol is used, gelation will notgenerally occur immediately; some solvent evaporation will be needed.

[0022] Generally, a molar ratio of water:alkoxide from about of 0.1:1 to10:1 is used. The amount of water utilized in the reaction is thatcalculated to hydrolyze the inorganic alkoxide in the reaction mixture.A ratio lower than that needed to hydrolyze the alkoxide species willresult in a partially hydrolyzed material, which in most cases willreach a gel point at a much slower rate, depending on the agingprocedure and the presence of atmospheric moisture.

[0023] The xerogels and aerogels that are used for the catalysts of thepresent invention comprise a matrix material derived from a solution ofthe matrix component incorporating the active catalyst component, whichis essentially derived from a dissolved component. A matrix is askeletal framework of oxides and oxyhydroxides (also referred to asoxide/hydroxide) derived from the hydrolysis and condensation ofalkoxides and other reagents. The framework typically comprises at least20 mole % or more of the total catalyst composition. The matrix materialcomprises magnesium, silicon, or aluminum oxyhydroxides, xerogels oraerogels, or mixtures thereof totaling from about 20 mole % to about99.9, preferably from 25 to 99 mole % of the catalyst composition.

[0024] The xerogels and aerogels thus produced can be described asprecursor salts dispersed in an oxide or oxyhydroxide matrix. Thehydroxyl content is at this point unknown. A theoretical maximumcorresponds to the valence of central metal atom. The molar H₂O:alkoxideratio can impact the final xerogel stoichiometry so that there will beresidual —OR groups in unaged gel. However, reaction with atmosphericmoisture will convert these to the corresponding —OH, and —O groups uponcontinued polymerization and dehydration. Aging, even under inertconditions, can also effect the condensation of the —OH, eliminatingH₂O, through continuation of cross linking and polymerization, i.e., gelformation.

[0025] Catalysts disclosed herein can also be prepared by destabilizingpre-formed aquasols to form gels. For example, aqueous solutions ofwater soluble salts of Cr, Al, Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be, Mg,Ca, Sr and Ba (e.g., Cr(NO₃)₃, Al(NO₃)₃, Zn(NO₃)₂, Sn(NO₃)₂, RhCl₃,LiNO₃, NaNO₃, KNO₃, RbNO₃, CsNO₃, Be(NO₃)₂, Mg(NO₃)₂, Ca(NO₃)₂,Sr(NO₃)₂, and Ba(NO₃)₂) are used. Other water soluble salts of Cr, Al,Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba can be used (e.g.,acetates, chlorides, nitrates, nitrites) also. These solutions are addedto colloids such as a colloidal aluminum, silicon or magnesium aquasolto destabilize the aquasol by altering solution pH or ionic strength.Commercially available colloids may also be used. In some cases, theaddition of acids (including nitric acid, acetic acid) or bases(including ammonium hydroxide) can also alter the pH of the solution andinduce a gel point. The resulting gel must be dried. Subsequent dryingsteps can be performed be supercritical extraction or conventionaldrying to produce an aerogel or xerogel material.

[0026] The catalysts of the present invention can also be prepared by asol gel process. Typically, magnesium, silicon, and aluminum alkoxides(including magnesium methoxide, silicon tetraethylorthosilicate,aluminum isopropoxide) are combined under an inert atmosphere. Acontrolled amount of aqueous solution containing salts selected from thegroup consisting of chromium Cr, Al, Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be,Mg, Ca, Sr and Ba (e.g., Cr(NO₃)₃, chromium acetate, chromium hydroxideacetate, Al(NO₃)₃, Zn(NO₃)₂, Sn(NO₃)₂, RhCl₃, LiNO₃, NaNO₃, KNO₃, RbNO₃,CsNO₃, Be(NO₃)₂, Mg(NO₃)₂, Ca(NO₃)₂, Sr(NO₃)₂, and Ba(NO₃)₂) are used.Other water soluble salts (for example, acetates, chlorides, nitrates,nitrites) of Cr, Al, Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr andBa can be added to induce a gel point. The material can beconventionally or supercritcally dried to produce a xerogel or aerogel.

[0027] After forming the gels of the present invention, it may benecessary to complete the gelation process with some aging of the gel.This aging can range form one minute to several days. Generally, thegels are aged at room temperature in air for at least several hours.

[0028] Removal of solvent from the gels can be accomplished by severalmethods. Removal by vacuum drying or heating in air results in theformation of a xerogel. An aerogel of the material can typically beformed by charging in a pressurized system such as an autoclave. The gelcontaining the solvent is placed in an autoclave where it can becontacted with a fluid above its critical temperature and pressure.Various fluids can be used at their critical temperature and pressurefor this purpose. For example, suitable fluids includefluorochlorocarbons typified by Freon® chlorofluorocarbons (e.g., Freon®11 (CCl₃F), 12 (CCl₂F₂) or 114 (CClF₂CClF₂), ammonia and carbon dioxide.

[0029] Using Freeze Dying:

[0030] Freeze drying procedures can accommodate several catalystcompositions, and are useful if the catalyst precursors are soluble inwater or other solvent which can be rapidly frozen. Precursor salts aredissolved in an appropriate amount of solvent to form a solution or finecolloid. The solution is then rapidly cooled and frozen by immersion ina suitable medium, such as liquid nitrogen. If the solution is rapidlyfrozen, the salts and other components will remain intimately mixed andwill not segregate to any significant degree. The frozen solid istransferred to a freeze drying chamber. The solution is kept frozenwhile water vapor is removed by evacuation. Refrigerated shelves areused to prevent thaw-out of the frozen solids during evacuation.

[0031] Freeze drying procedures for catalysts compositions in thepresent invention involve the use of soluble precursor salts. Solutionconcentrations can vary widely, and can range from 0.1 M to 10 M,depending on the solubility of the precursor salts used. Solutions arepreferably rapidly frozen (<<1 min) to preserve intimate mixing of theprecursor salt components. Evacuation times can vary from day(s) orweek(s), depending on the quantity of solvent to be removed. Catalystmaterials are typically calcined, either ex situ or in situ to producethe final, active form. Catalyst precursor solutions can also be soaked,added or impregnated into porous catalyst monoliths, frozen, dried andcalcined as described above.

[0032] In a typical embodiment of the present invention, water solublesalts of Cr, Al, Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba(e.g., Cr(NO₃)₃, Al(NO₃)₃, Zn(NO₃)₂, Sn(NO₃)₂, RhCl₃, LiNO₃, NaNO₃,KNO₃, RbNO₃, CsNO₃, Be(NO₃)₂, Mg(NO₃)₂, Ca(NO₃)₂, Sr(NO₃)₂, andBa(NO₃)₂) are used. The water-soluble salts are dissolved in water priorto freeze drying. Other water soluble salts of Cr, Al, Zn, Sn, Rh, Li,Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba (e.g., acetates, chlorides,nitrates, nitrites) and colloids of aluminum oxide, silicon oxide, ormetal colloids containing Rh or Cr also can be used. Solution formationis preferable, but not required. Other solvent systems can be used, ifthey can be frozen. The solution is then rapidly frozen by immersion ina suitable medium, such as liquid nitrogen. When the resultingcombination is frozen rapidly, the salts and other components willremain intimately mixed and, generally, will not segregate to anysignificant degree. The frozen solid is then dried under vacuum andoptionally, heated in air, or calcined, to decompose the salt present. Afreeze drying chamber may be used for drying.

[0033] Using Spray Drying

[0034] Spray drying procedures involve the use of solutions, colloids orslurries containing catalyst precursors or catalyst compounds. Thetechnique consists of atomization of these liquids (usually but notexclusively aqueous) into a spray, and contact between spray and dryingmedium (usually hot air) resulting in moisture evaporation. The dryingof the spray proceeds until the desired moisture content in the driedparticles is obtain, and the product is recovered by suitable separationtechniques (usually cyclone separation). A detailed description of spraydrying methods can be found in “Spray Drying Handbook”, 4^(th) editionby K Masters (Longman Scientific and Technical, John Wiley and Sons,N.Y) c. 1985.

[0035] Using Spray Roasting

[0036] Spray roasting also involves the use of solutions or colloids,but generally involves drying and calcination (at higher temperatures)in one process step to produce catalyst powders.

[0037] Use of Disclosed Catalysts in Dehydrogenation Processes

[0038] The hydrocarbon feed that can be used in the present inventionincludes any C₂ to C₁₀ hydrocarbon with propane, isobutane and isooctane(2,2,4-trimethylpentane) being preferred. The process of the presentinvention can be carried out in fixed, moving, fluidized, ebullating orentrained bed reactors.

[0039] The catalysts of this invention can be periodically regeneratedto remove coke. The regeneration is done by conventional techniques ofcarbon removal such as heating with an oxygen-containing gas, preferablyair.

[0040] The gas hourly space velocity (GHSV) of the feed gas generally isin the range of from about 100 to about 3000 cc hydrocarbon feed/cccatalyst/hour, preferably from about 500 to about 1000 cc/cc/hour. Theoperating pressure is generally in the range of from about 7 kPa toabout 700 kPa, preferably from about 7 kPa to about 400 kPa. Thereaction temperature generally is in the range of from about 450° C. toabout 800° C., preferably from about 500° C. to 600° C.

[0041] The less saturated hydrocarbon reaction products of thisinvention can be separated by conventional means such as distillation,membrane separation and absorption.

EXAMPLES

[0042] General Procedure for Catalyst Testing

[0043] Catalyst tests were performed in a fixed bed continuous flowquartz reactor with 6.4 mm id. The catalyst charge was 2.0 mL of −12/+20mesh (−1.68/+0.84 mm) granules for Examples 1 to 5, 9 and ComparativeExamples A and D; 1.0 mL of −12/+20 mesh (−1.68/+0.84 mm) granules forExamples 7, 8 and Comparative Examples B and C; 0.5 mL of −12/+20 mesh(−1.68/+0.84 mm) granules for Example 6. The reactor tube was heated ina tube furnace to 550° C. in flowing nitrogen until the temperature wasstable. A thermocouple inside the catalyst bed was used to measuretemperature. Once the desired temperature was achieved, a feedconsisting of 50% isobutane/50% nitrogen (Examples 4 to 9 or a feedconsisting of 50% propane/50% nitrogen (Examples 1, 2, 3) were passedover the catalyst bed. The contact time was 3.2 seconds for Examples 1,2, 3, 7, 8, 9. The contact time was 1.6 seconds for Examples 4, 5, 6.The entire product stream was analyzed on-line using sampling valves andan HP5890 chromatogram (TCD)/HP 5971 mass selective detector.

[0044] The results of the catalyst tests are shown in Tables 1 (propanedehydrogenation). and 2 (isobutane dehydrogenation). Legend C₃ isCH₃CH₂CH₃ C₃= is CH₂ = CHCH₃ iC4 is (CH₃)₂CHCH₃ iC4 = is (CH₃)₂C = CH₂Conv. is conversion Sel. is selectivity

EXAMPLES Example 1 Cr_(0.25)Zn_(0.25)Al_(0.5)

[0045] A 1 M aqueous solution of Cr(NO₃)₃.9H₂O (23.346 mL) wassimultaneously combined with an aqueous solution of ZnCl₂ (31.981 mL,0.73 M), preformed AlO_(1.5) aquasol (10.003 mL, 4.67 M) and 0.1 M HCl(4.660 mL). The material appeared gel-like within minutes. It was driedunder vacuum for 5 hours (120° C.) and then calcined at 300° C. in airfor 3 hours prior to use. The material was pelletized and granulated on−10/+20 mesh (−2.0/+0.84 mm) screens prior to use.

Example 2 Rh_(0.01)Cr_(0.1)Ce_(0.89)

[0046] A 0.02 M RhCl₃ solution (32 mL, prepared using 6 M HCl) wascombined with a 2.5603 M (with respect to chromium) aqueous solution ofCr₃(OH)₂(Ac)₇ (2.45 mL) and a 0.7262 M cerium nitrate solution(Ce(NO₃)₃.6H₂O, 78.14 mL). The material was frozen in liquid nitrogenand evacuated for at least five days prior to calcination. The powderwas calcined at 525° C. in air for 1 hour. The material was pelletizedand granulated on −10/+20 mesh (−2.0/+0.84 mm) screens prior to use.

Example 3 Cr_(0.25)Al_(0.25)Sn_(0.5)

[0047] The same procedure as described in Example 1 was used except thatthe following amounts of materials were used: 1 M aqueous solution ofCr(NO₃)₃.9H₂O (24.879); 0.8438 aqueous solution of SnCl₂ (29.485 mL,0.73 M); preformed AlO_(1.5) aquasol (10.66 mL, 4.67 M) and 0.1 M HCl(4.976 mL). The material appeared gel-like within minutes. It was driedunder vacuum for 5 hours (120° C.) and then calcined at 300° C. in airfor 3 hours. The material was pelletized and granulated on −10/+20 mesh(−2.0/+0.84 mm) screens prior to use.

Example 4 Mg_(0.04)Cr_(0.2)Si_(0.76)

[0048] A 0.699 M magnesium methoxide solution in methanol (12.856 mL)was added to a 150 mL petri dish along with tetraethylorthosilicate (60vol. % in ethanol, 63.471 mL) and ethanol (6.125 mL) with gentleswirling. In a second step, a 2.5603 M (with respect to chromium)aqueous chromium hydroxide acetate (17.549 mL) was added. The materialreached its gel point very quickly, and was dark purple in color. It wasdried under vacuum for 5 hours (120° C.) and then calcined at −350° C.in air for 5 hours. The material was pelletized and granulated on−10/+20 mesh (−2.0/+0.84 mm) screens prior to use.

Example 5 Cr_(0.2)Si_(0.8)

[0049] An identical procedure as described in Example 4 was used withthe following amounts of materials: 2.5603 M (with respect to chromium)aqueous chromium hydroxide acetate (20.344 mL); tetraethylorthosilicate(60 vol. % in ethanol, 77.455 mL). A homogeneous gel formed, which wasdark purple in color. It was dried under vacuum for 5 hours (120° C.)and then calcined at 350° C. in air for 5 hours. The material waspelletized and granulated on −10/+20 mesh (−2.0/+0.84 mm) screens priorto use.

Example 6 Rh_(0.01)Ce_(0.99)

[0050] A solution of 0.02 M RhCl₃ (6.943 mL) (prepared by dissolving thesalt in 6 M HCl) was added to an aqueous solution of 0.7261 MCe(NO₃)₃.6H₂O (38.057 mL). The solution was rapidly frozen in liquidnitrogen, evacuated to drying on a freeze dryer, and the free flowingpowder was calcined to 350° C. for 5 hours in air prior to use.

Example 7 Cr_(0.25)Zn_(0.25)Al_(0.5)

[0051] The Example 1 catalyst was used.

Example 8 Rh_(0.01)Cr_(0.1)Ce_(0.89)

[0052] The Example 2 catalyst was used.

Example 9

[0053] The Example 2 catalyst was used. TABLE 1 PROPANE DEHYDROGENATIONEx. % C₃ % C₃₌ % C₂ % CH₄ % Others No. Conv. Sel. Sel. Sel. Sel. 1 39.488.3 9.8 0.1 1.9 2 7.0 84.8 9.6 0 5.1 3 7.2 40.0 30.3 0 29.7

[0054] TABLE 2 ISOBUTANE DEHYDROGENATION Ex. % iC₄ % iC₄= % CH₄ % C₂-C₄% Others No. Conv. Sel. Sel. Sel. Sel. 4 45.5 84.1 8.9 7.1 0 5 54.0 82.19.6 8.4 0 6 13.1 42.4 18.8 38.9 0 7 72.6 56.7 18.5 23.5 1.4 8 15.3 83.50.6 14.7 1.3 9 11.6 51.3 3.0 25.3 20.5

What is claimed is:
 1. A composition of matter having the formulaCr_(a)A_(b)B_(c)(O_(1−z(OH)) _(2z))_(y), wherein a+b+c=1; wherein A isan element selected from the group consisting of Zn, Sn, Rh, Li, Na, K,Rb, Cs, Be, Mg, Ca, Sr and Ba; wherein B is at least one elementselected from the group consisting of Al, Si and Mg; wherein a isgreater than 0.01 but less than 0.5; b is greater than 0.01 but lessthan or equal to 0.5; c is greater than 0.2 but less than or equal to0.999; wherein y is determined by the sum of the oxidation states of Cr,A and B individually multiplied by the corresponding stoichiometriccoefficent a, b, or c, and said sum then divided by 2; and z is greaterthan or equal to 0 but less than or equal to
 2. 2. A composition ofclaim 1 wherein said composition is prepared from C₁-C₂₀ metalalkoxides.
 3. The composition of claim 1 wherein said composition isprepared from C₁-C₄ metal alkoxides.
 4. The composition of claim 3wherein the composition is prepared from aluminum isopropoxide.
 5. Aprocess of making the composition of claim 1, said process comprising:preparing a solution of a soluble salt comprising at least one metalselected from the group consisting of Cr, Al, Sn, Rh, Li, Na, K, Rb, Cs,Be, Mg, Ca, Sr and Ba; adding said solution to a non-aqueous solution ofa soluble salt comprising at least one metal selected from the groupconsisting of Cr, Al, Si, Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr,and Ba to form a gel; drying said gel to produce a xerogel or aerogel.6. A process for making the composition of claim 1, said processcomprising: preparing a non-aqueous solution of a soluble saltcomprising at least one metal selected from the group consisting of Cr,Al, Si, Zn, Sn, Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba and atleast one alkoxide selected from the group consisting of magnesium,silicon, and aluminum alkoxides in an inert atmosphere; adding water orother protic solvents, optionally containing at least one dissolvedmetal selected from the group consisting of Cr, Al, Zn, Sn, Rh, Li, Na,K, Rb, Cs, Be, Mg, Ca, Sr, and Ba, to form a gel; and drying said gel toproduce a xerogel or aerogel.
 7. A process of making the composition ofclaim 1, said process comprising: contacting a solution comprising watersoluble salt selected from the group from the group consisting of Cr,Al, Zn, Sn. Rh, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, and Ba with a colloidselected from the group consisting of magnesium, aluminum and silicon;optionally, adding a pH altering solution whereby the colloid isdestabilized; optionally, removing solvent whereby the colloid isdestabilized; and drying said gel to produce a xerogel or aerogel.
 8. Aprocess of making the composition of claim 1 said process comprising:combining, in the presence of chromium, a solution comprising at leastone of element A and at least one of element B to form a solution or asuspension; freezing rapidly the combination of the first step; dryingthe frozen solid under vacuum; and optionally, heating the resultingsolid to decompose the salts.
 9. A process for converting at least oneC₂ to C₁₀ hydrocarbon to less saturated hydrocarbons, said processcomprising the step of: contacting at least one C₂ to C₁₀ hydrocarbonfeed with at least one catalyst selected from the group consisting ofCr_(a)A_(b)B_(c)(O_(1−z)(OH)_(2z))_(y), wherein a+b+c=1; wherein A is anelement selected from the group consisting of Zn, Sn, Rh, Li, Na, K, Rb,Cs, Be, Mg, Ca, Sr and Ba; wherein B is at least one element selectedfrom the group consisting of Al, Si and Mg;wherein a is greater than0.01 but less than 0.5; wherein b is greater than 0.01 but less than orequal to 0.5; wherein c is greater than 0.2 but less than or equal to0.999; wherein y is determined by the sum of the oxidation states of Cr,A and B individually multiplied by the corresponding stoichiometriccoefficent a, b, or c, and said sum then divided by 2; and wherein z isgreater than or equal to 0 but less than or equal to 2; with a catalystcomposition comprising rhodium and rare earth oxides.
 10. The process ofclaim 9 wherein said hydrocarbon feed is selected from the groupconsisting of propane, isobutane and isooctane.
 11. The process of claim10 wherein said contacting is done at a temperature of from about 450°C. to about 800° C., at a pressure of from about 7 kPa to about 700 kPa,and said hydrocarbon feed has a gas hourly space velocity from about 100cc hydrocarbon feed per cc catalyst per hour to about 3000 cchydrocarbon feed per cc catalyst per hour.
 12. The process of claim 9wherein said contacting is done at a temperature of from about 500° C.to about 600° C.
 13. The process of claim 9 wherein said contacting isdone at a pressure of from about 7 kPa to about 400 kPa.
 14. The processof claim 9 wherein said hydrocarbon feed has a gas hourly space velocityfrom about 500 cc hydrocarbon feed per cc catalyst per hour to about1000 cc hydrocarbon feed per cc catalyst per hour.